<?php

/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_Gdata
 * @subpackage App
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @version    $Id: App.php 18951 2009-11-12 16:26:19Z alexander $
 */

/**
 * Zend_Gdata_Feed
 */
require_once 'Zend/Gdata/App/Feed.php';

/**
 * Zend_Gdata_Http_Client
 */
require_once 'Zend/Http/Client.php';

/**
 * Zend_Version
 */
require_once 'Zend/Version.php';

/**
 * Zend_Gdata_App_MediaSource
 */
require_once 'Zend/Gdata/App/MediaSource.php';

/**
 * Provides Atom Publishing Protocol (APP) functionality.  This class and all
 * other components of Zend_Gdata_App are designed to work independently from
 * other Zend_Gdata components in order to interact with generic APP services.
 *
 * @category   Zend
 * @package    Zend_Gdata
 * @subpackage App
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 */
class Zend_Gdata_App
{

	/** Default major protocol version.
	 *
	 * @see _majorProtocolVersion
	 */
	const DEFAULT_MAJOR_PROTOCOL_VERSION = 1;

	/** Default minor protocol version.
	 *
	 * @see _minorProtocolVersion
	 */
	const DEFAULT_MINOR_PROTOCOL_VERSION = null;

	/**
	 * Client object used to communicate
	 *
	 * @var Zend_Http_Client
	 */
	protected $_httpClient;

	/**
	 * Client object used to communicate in static context
	 *
	 * @var Zend_Http_Client
	 */
	protected static $_staticHttpClient = null;

	/**
	 * Override HTTP PUT and DELETE request methods?
	 *
	 * @var boolean
	 */
	protected static $_httpMethodOverride = false;

	/**
	 * Enable gzipped responses?
	 *
	 * @var boolean
	 */
	protected static $_gzipEnabled = false;

	/**
	 * Use verbose exception messages.  In the case of HTTP errors,
	 * use the body of the HTTP response in the exception message.
	 *
	 * @var boolean
	 */
	protected static $_verboseExceptionMessages = true;

	/**
	 * Default URI to which to POST.
	 *
	 * @var string
	 */
	protected $_defaultPostUri = null;

	/**
	 * Packages to search for classes when using magic __call method, in order.
	 *
	 * @var array
	 */
	protected $_registeredPackages = array(
            'Zend_Gdata_App_Extension',
            'Zend_Gdata_App');

	/**
	 * Maximum number of redirects to follow during HTTP operations
	 *
	 * @var int
	 */
	protected static $_maxRedirects = 5;

	/**
	 * Indicates the major protocol version that should be used.
	 * At present, recognized values are either 1 or 2. However, any integer
	 * value >= 1 is considered valid.
	 *
	 * Under most circumtances, this will be automatically set by
	 * Zend_Gdata_App subclasses.
	 *
	 * @see setMajorProtocolVersion()
	 * @see getMajorProtocolVersion()
	 */
	protected $_majorProtocolVersion;

	/**
	 * Indicates the minor protocol version that should be used. Can be set
	 * to either an integer >= 0, or NULL if no minor version should be sent
	 * to the server.
	 *
	 * At present, this field is not used by any Google services, but may be
	 * used in the future.
	 *
	 * Under most circumtances, this will be automatically set by
	 * Zend_Gdata_App subclasses.
	 *
	 * @see setMinorProtocolVersion()
	 * @see getMinorProtocolVersion()
	 */
	protected $_minorProtocolVersion;

	/**
	 * Whether we want to use XML to object mapping when fetching data.
	 *
	 * @var boolean
	 */
	protected $_useObjectMapping = true;

	/**
	 * Create Gdata object
	 *
	 * @param Zend_Http_Client $client
	 * @param string $applicationId
	 */
	public function __construct($client = null, $applicationId = 'MyCompany-MyApp-1.0')
	{
		$this->setHttpClient($client, $applicationId);
		// Set default protocol version. Subclasses should override this as
		// needed once a given service supports a new version.
		$this->setMajorProtocolVersion(self::DEFAULT_MAJOR_PROTOCOL_VERSION);
		$this->setMinorProtocolVersion(self::DEFAULT_MINOR_PROTOCOL_VERSION);
	}

	/**
	 * Adds a Zend Framework package to the $_registeredPackages array.
	 * This array is searched when using the magic __call method below
	 * to instantiante new objects.
	 *
	 * @param string $name The name of the package (eg Zend_Gdata_App)
	 * @return void
	 */
	public function registerPackage($name)
	{
		array_unshift($this->_registeredPackages, $name);
	}

	/**
	 * Retrieve feed as string or object
	 *
	 * @param string $uri The uri from which to retrieve the feed
	 * @param string $className The class which is used as the return type
	 * @return string|Zend_Gdata_App_Feed Returns string only if the object
	 *                                    mapping has been disabled explicitly
	 *                                    by passing false to the
	 *                                    useObjectMapping() function.
	 */
	public function getFeed($uri, $className='Zend_Gdata_App_Feed')
	{
		return $this->importUrl($uri, $className, null);
	}

	/**
	 * Retrieve entry as string or object
	 *
	 * @param string $uri
	 * @param string $className The class which is used as the return type
	 * @return string|Zend_Gdata_App_Entry Returns string only if the object
	 *                                     mapping has been disabled explicitly
	 *                                     by passing false to the
	 *                                     useObjectMapping() function.
	 */
	public function getEntry($uri, $className='Zend_Gdata_App_Entry')
	{
		return $this->importUrl($uri, $className, null);
	}

	/**
	 * Get the Zend_Http_Client object used for communication
	 *
	 * @return Zend_Http_Client
	 */
	public function getHttpClient()
	{
		return $this->_httpClient;
	}

	/**
	 * Set the Zend_Http_Client object used for communication
	 *
	 * @param Zend_Http_Client $client The client to use for communication
	 * @throws Zend_Gdata_App_HttpException
	 * @return Zend_Gdata_App Provides a fluent interface
	 */
	public function setHttpClient($client,
	$applicationId = 'MyCompany-MyApp-1.0')
	{
		if ($client === null) {
			$client = new Zend_Http_Client();
		}
		if (!$client instanceof Zend_Http_Client) {
			require_once 'Zend/Gdata/App/HttpException.php';
			throw new Zend_Gdata_App_HttpException(
                'Argument is not an instance of Zend_Http_Client.');
		}
		$userAgent = $applicationId . ' Zend_Framework_Gdata/' .
		Zend_Version::VERSION;
		$client->setHeaders('User-Agent', $userAgent);
		$client->setConfig(array(
            'strictredirects' => true
		)
		);
		$this->_httpClient = $client;
		Zend_Gdata::setStaticHttpClient($client);
		return $this;
	}

	/**
	 * Set the static HTTP client instance
	 *
	 * Sets the static HTTP client object to use for retrieving the feed.
	 *
	 * @param  Zend_Http_Client $httpClient
	 * @return void
	 */
	public static function setStaticHttpClient(Zend_Http_Client $httpClient)
	{
		self::$_staticHttpClient = $httpClient;
	}


	/**
	 * Gets the HTTP client object. If none is set, a new Zend_Http_Client will be used.
	 *
	 * @return Zend_Http_Client
	 */
	public static function getStaticHttpClient()
	{
		if (!self::$_staticHttpClient instanceof Zend_Http_Client) {
			$client = new Zend_Http_Client();
			$userAgent = 'Zend_Framework_Gdata/' . Zend_Version::VERSION;
			$client->setHeaders('User-Agent', $userAgent);
			$client->setConfig(array(
                'strictredirects' => true
			)
			);
			self::$_staticHttpClient = $client;
		}
		return self::$_staticHttpClient;
	}

	/**
	 * Toggle using POST instead of PUT and DELETE HTTP methods
	 *
	 * Some feed implementations do not accept PUT and DELETE HTTP
	 * methods, or they can't be used because of proxies or other
	 * measures. This allows turning on using POST where PUT and
	 * DELETE would normally be used; in addition, an
	 * X-Method-Override header will be sent with a value of PUT or
	 * DELETE as appropriate.
	 *
	 * @param  boolean $override Whether to override PUT and DELETE with POST.
	 * @return void
	 */
	public static function setHttpMethodOverride($override = true)
	{
		self::$_httpMethodOverride = $override;
	}

	/**
	 * Get the HTTP override state
	 *
	 * @return boolean
	 */
	public static function getHttpMethodOverride()
	{
		return self::$_httpMethodOverride;
	}

	/**
	 * Toggle requesting gzip encoded responses
	 *
	 * @param  boolean $enabled Whether or not to enable gzipped responses
	 * @return void
	 */
	public static function setGzipEnabled($enabled = false)
	{
		if ($enabled && !function_exists('gzinflate')) {
			require_once 'Zend/Gdata/App/InvalidArgumentException.php';
			throw new Zend_Gdata_App_InvalidArgumentException(
                    'You cannot enable gzipped responses if the zlib module ' .
                    'is not enabled in your PHP installation.');

		}
		self::$_gzipEnabled = $enabled;
	}

	/**
	 * Get the HTTP override state
	 *
	 * @return boolean
	 */
	public static function getGzipEnabled()
	{
		return self::$_gzipEnabled;
	}

	/**
	 * Get whether to use verbose exception messages
	 *
	 * In the case of HTTP errors,  use the body of the HTTP response
	 * in the exception message.
	 *
	 * @return boolean
	 */
	public static function getVerboseExceptionMessages()
	{
		return self::$_verboseExceptionMessages;
	}

	/**
	 * Set whether to use verbose exception messages
	 *
	 * In the case of HTTP errors, use the body of the HTTP response
	 * in the exception message.
	 *
	 * @param boolean $verbose Whether to use verbose exception messages
	 */
	public static function setVerboseExceptionMessages($verbose)
	{
		self::$_verboseExceptionMessages = $verbose;
	}

	/**
	 * Set the maximum number of redirects to follow during HTTP operations
	 *
	 * @param int $maxRedirects Maximum number of redirects to follow
	 * @return void
	 */
	public static function setMaxRedirects($maxRedirects)
	{
		self::$_maxRedirects = $maxRedirects;
	}

	/**
	 * Get the maximum number of redirects to follow during HTTP operations
	 *
	 * @return int Maximum number of redirects to follow
	 */
	public static function getMaxRedirects()
	{
		return self::$_maxRedirects;
	}

	/**
	 * Set the major protocol version that should be used. Values < 1 will
	 * cause a Zend_Gdata_App_InvalidArgumentException to be thrown.
	 *
	 * @see _majorProtocolVersion
	 * @param int $value The major protocol version to use.
	 * @throws Zend_Gdata_App_InvalidArgumentException
	 */
	public function setMajorProtocolVersion($value)
	{
		if (!($value >= 1)) {
			require_once('Zend/Gdata/App/InvalidArgumentException.php');
			throw new Zend_Gdata_App_InvalidArgumentException(
                    'Major protocol version must be >= 1');
		}
		$this->_majorProtocolVersion = $value;
	}

	/**
	 * Get the major protocol version that is in use.
	 *
	 * @see _majorProtocolVersion
	 * @return int The major protocol version in use.
	 */
	public function getMajorProtocolVersion()
	{
		return $this->_majorProtocolVersion;
	}

	/**
	 * Set the minor protocol version that should be used. If set to NULL, no
	 * minor protocol version will be sent to the server. Values < 0 will
	 * cause a Zend_Gdata_App_InvalidArgumentException to be thrown.
	 *
	 * @see _minorProtocolVersion
	 * @param (int|NULL) $value The minor protocol version to use.
	 * @throws Zend_Gdata_App_InvalidArgumentException
	 */
	public function setMinorProtocolVersion($value)
	{
		if (!($value >= 0)) {
			require_once('Zend/Gdata/App/InvalidArgumentException.php');
			throw new Zend_Gdata_App_InvalidArgumentException(
                    'Minor protocol version must be >= 0');
		}
		$this->_minorProtocolVersion = $value;
	}

	/**
	 * Get the minor protocol version that is in use.
	 *
	 * @see _minorProtocolVersion
	 * @return (int|NULL) The major protocol version in use, or NULL if no
	 *         minor version is specified.
	 */
	public function getMinorProtocolVersion()
	{
		return $this->_minorProtocolVersion;
	}

	/**
	 * Provides pre-processing for HTTP requests to APP services.
	 *
	 * 1. Checks the $data element and, if it's an entry, extracts the XML,
	 *    multipart data, edit link (PUT,DELETE), etc.
	 * 2. If $data is a string, sets the default content-type  header as
	 *    'application/atom+xml' if it's not already been set.
	 * 3. Adds a x-http-method override header and changes the HTTP method
	 *    to 'POST' if necessary as per getHttpMethodOverride()
	 *
	 * @param string $method The HTTP method for the request - 'GET', 'POST',
	 *                       'PUT', 'DELETE'
	 * @param string $url The URL to which this request is being performed,
	 *                    or null if found in $data
	 * @param array $headers An associative array of HTTP headers for this
	 *                       request
	 * @param mixed $data The Zend_Gdata_App_Entry or XML for the
	 *                    body of the request
	 * @param string $contentTypeOverride The override value for the
	 *                                    content type of the request body
	 * @return array An associative array containing the determined
	 *               'method', 'url', 'data', 'headers', 'contentType'
	 */
	public function prepareRequest($method,
	$url = null,
	$headers = array(),
	$data = null,
	$contentTypeOverride = null)
	{
		// As a convenience, if $headers is null, we'll convert it back to
		// an empty array.
		if ($headers === null) {
			$headers = array();
		}

		$rawData = null;
		$finalContentType = null;
		if ($url == null) {
			$url = $this->_defaultPostUri;
		}

		if (is_string($data)) {
			$rawData = $data;
			if ($contentTypeOverride === null) {
				$finalContentType = 'application/atom+xml';
			}
		} elseif ($data instanceof Zend_Gdata_App_MediaEntry) {
			$rawData = $data->encode();
			if ($data->getMediaSource() !== null) {
				$finalContentType = $rawData->getContentType();
				$headers['MIME-version'] = '1.0';
				$headers['Slug'] = $data->getMediaSource()->getSlug();
			} else {
				$finalContentType = 'application/atom+xml';
			}
			if ($method == 'PUT' || $method == 'DELETE') {
				$editLink = $data->getEditLink();
				if ($editLink != null && $url == null) {
					$url = $editLink->getHref();
				}
			}
		} elseif ($data instanceof Zend_Gdata_App_Entry) {
			$rawData = $data->saveXML();
			$finalContentType = 'application/atom+xml';
			if ($method == 'PUT' || $method == 'DELETE') {
				$editLink = $data->getEditLink();
				if ($editLink != null) {
					$url = $editLink->getHref();
				}
			}
		} elseif ($data instanceof Zend_Gdata_App_MediaSource) {
			$rawData = $data->encode();
			if ($data->getSlug() !== null) {
				$headers['Slug'] = $data->getSlug();
			}
			$finalContentType = $data->getContentType();
		}

		if ($method == 'DELETE') {
			$rawData = null;
		}

		// Set an If-Match header if:
		//   - This isn't a DELETE
		//   - If this isn't a GET, the Etag isn't weak
		//   - A similar header (If-Match/If-None-Match) hasn't already been
		//     set.
		if ($method != 'DELETE' && (
		!array_key_exists('If-Match', $headers) &&
		!array_key_exists('If-None-Match', $headers)
		) ) {
			$allowWeak = $method == 'GET';
			if ($ifMatchHeader = $this->generateIfMatchHeaderData(
			$data, $allowWeak)) {
				$headers['If-Match'] = $ifMatchHeader;
			}
		}

		if ($method != 'POST' && $method != 'GET' && Zend_Gdata_App::getHttpMethodOverride()) {
			$headers['x-http-method-override'] = $method;
			$method = 'POST';
		} else {
			$headers['x-http-method-override'] = null;
		}

		if ($contentTypeOverride != null) {
			$finalContentType = $contentTypeOverride;
		}

		return array('method' => $method, 'url' => $url,
            'data' => $rawData, 'headers' => $headers,
            'contentType' => $finalContentType);
	}

	/**
	 * Performs a HTTP request using the specified method
	 *
	 * @param string $method The HTTP method for the request - 'GET', 'POST',
	 *                       'PUT', 'DELETE'
	 * @param string $url The URL to which this request is being performed
	 * @param array $headers An associative array of HTTP headers
	 *                       for this request
	 * @param string $body The body of the HTTP request
	 * @param string $contentType The value for the content type
	 *                                of the request body
	 * @param int $remainingRedirects Number of redirects to follow if request
	 *                              s results in one
	 * @return Zend_Http_Response The response object
	 */
	public function performHttpRequest($method, $url, $headers = null,
	$body = null, $contentType = null, $remainingRedirects = null)
	{
		require_once 'Zend/Http/Client/Exception.php';
		if ($remainingRedirects === null) {
			$remainingRedirects = self::getMaxRedirects();
		}
		if ($headers === null) {
			$headers = array();
		}
		// Append a Gdata version header if protocol v2 or higher is in use.
		// (Protocol v1 does not use this header.)
		$major = $this->getMajorProtocolVersion();
		$minor = $this->getMinorProtocolVersion();
		if ($major >= 2) {
			$headers['GData-Version'] = $major +
			(($minor === null) ? '.' + $minor : '');
		}

		// check the overridden method
		if (($method == 'POST' || $method == 'PUT') && $body === null &&
		$headers['x-http-method-override'] != 'DELETE') {
			require_once 'Zend/Gdata/App/InvalidArgumentException.php';
			throw new Zend_Gdata_App_InvalidArgumentException(
                        'You must specify the data to post as either a ' .
                        'string or a child of Zend_Gdata_App_Entry');
		}
		if ($url === null) {
			require_once 'Zend/Gdata/App/InvalidArgumentException.php';
			throw new Zend_Gdata_App_InvalidArgumentException(
                'You must specify an URI to which to post.');
		}
		$headers['Content-Type'] = $contentType;
		if (Zend_Gdata_App::getGzipEnabled()) {
			// some services require the word 'gzip' to be in the user-agent
			// header in addition to the accept-encoding header
			if (strpos($this->_httpClient->getHeader('User-Agent'),
                'gzip') === false) {
			$headers['User-Agent'] =
			$this->_httpClient->getHeader('User-Agent') . ' (gzip)';
                }
                $headers['Accept-encoding'] = 'gzip, deflate';
		} else {
			$headers['Accept-encoding'] = 'identity';
		}

		// Make sure the HTTP client object is 'clean' before making a request
		// In addition to standard headers to reset via resetParameters(),
		// also reset the Slug header
		$this->_httpClient->resetParameters();
		$this->_httpClient->setHeaders('Slug', null);

		// Set the params for the new request to be performed
		$this->_httpClient->setHeaders($headers);
		$this->_httpClient->setUri($url);
		$this->_httpClient->setConfig(array('maxredirects' => 0));

		// Set the proper adapter if we are handling a streaming upload
		$usingMimeStream = false;
		$oldHttpAdapter = null;

		if ($body instanceof Zend_Gdata_MediaMimeStream) {
			$usingMimeStream = true;
			$this->_httpClient->setRawDataStream($body, $contentType);
			$oldHttpAdapter = $this->_httpClient->getAdapter();

			if ($oldHttpAdapter instanceof Zend_Http_Client_Adapter_Proxy) {
				require_once 'Zend/Gdata/HttpAdapterStreamingProxy.php';
				$newAdapter = new Zend_Gdata_HttpAdapterStreamingProxy();
			} else {
				require_once 'Zend/Gdata/HttpAdapterStreamingSocket.php';
				$newAdapter = new Zend_Gdata_HttpAdapterStreamingSocket();
			}
			$this->_httpClient->setAdapter($newAdapter);
		} else {
			$this->_httpClient->setRawData($body, $contentType);
		}

		try {
			$response = $this->_httpClient->request($method);
			// reset adapter
			if ($usingMimeStream) {
				$this->_httpClient->setAdapter($oldHttpAdapter);
			}
		} catch (Zend_Http_Client_Exception $e) {
			// reset adapter
			if ($usingMimeStream) {
				$this->_httpClient->setAdapter($oldHttpAdapter);
			}
			require_once 'Zend/Gdata/App/HttpException.php';
			throw new Zend_Gdata_App_HttpException($e->getMessage(), $e);
		}
		if ($response->isRedirect() && $response->getStatus() != '304') {
			if ($remainingRedirects > 0) {
				$newUrl = $response->getHeader('Location');
				$response = $this->performHttpRequest(
				$method, $newUrl, $headers, $body,
				$contentType, $remainingRedirects);
			} else {
				require_once 'Zend/Gdata/App/HttpException.php';
				throw new Zend_Gdata_App_HttpException(
                        'Number of redirects exceeds maximum', null, $response);
			}
		}
		if (!$response->isSuccessful()) {
			require_once 'Zend/Gdata/App/HttpException.php';
			$exceptionMessage = 'Expected response code 200, got ' .
			$response->getStatus();
			if (self::getVerboseExceptionMessages()) {
				$exceptionMessage .= "\n" . $response->getBody();
			}
			$exception = new Zend_Gdata_App_HttpException($exceptionMessage);
			$exception->setResponse($response);
			throw $exception;
		}
		return $response;
	}

	/**
	 * Imports a feed located at $uri.
	 *
	 * @param  string $uri
	 * @param  Zend_Http_Client $client The client used for communication
	 * @param  string $className The class which is used as the return type
	 * @throws Zend_Gdata_App_Exception
	 * @return string|Zend_Gdata_App_Feed Returns string only if the object
	 *                                    mapping has been disabled explicitly
	 *                                    by passing false to the
	 *                                    useObjectMapping() function.
	 */
	public static function import($uri, $client = null,
	$className='Zend_Gdata_App_Feed')
	{
		$app = new Zend_Gdata_App($client);
		$requestData = $app->prepareRequest('GET', $uri);
		$response = $app->performHttpRequest(
		$requestData['method'], $requestData['url']);

		$feedContent = $response->getBody();
		if (!$this->_useObjectMapping) {
			return $feedContent;
		}
		$feed = self::importString($feedContent, $className);
		if ($client != null) {
			$feed->setHttpClient($client);
		}
		return $feed;
	}

	/**
	 * Imports the specified URL (non-statically).
	 *
	 * @param  string $url The URL to import
	 * @param  string $className The class which is used as the return type
	 * @param array $extraHeaders Extra headers to add to the request, as an
	 *        array of string-based key/value pairs.
	 * @throws Zend_Gdata_App_Exception
	 * @return string|Zend_Gdata_App_Feed Returns string only if the object
	 *                                    mapping has been disabled explicitly
	 *                                    by passing false to the
	 *                                    useObjectMapping() function.
	 */
	public function importUrl($url, $className='Zend_Gdata_App_Feed',
	$extraHeaders = array())
	{
		$response = $this->get($url, $extraHeaders);

		$feedContent = $response->getBody();
		if (!$this->_useObjectMapping) {
			return $feedContent;
		}

		$protocolVersionStr = $response->getHeader('GData-Version');
		$majorProtocolVersion = null;
		$minorProtocolVersion = null;
		if ($protocolVersionStr !== null) {
			// Extract protocol major and minor version from header
			$delimiterPos = strpos($protocolVersionStr, '.');
			$length = strlen($protocolVersionStr);
			$major = substr($protocolVersionStr, 0, $delimiterPos);
			$minor = substr($protocolVersionStr, $delimiterPos + 1, $length);
			$majorProtocolVersion = $major;
			$minorProtocolVersion = $minor;
		}

		$feed = self::importString($feedContent, $className,
		$majorProtocolVersion, $minorProtocolVersion);
		if ($this->getHttpClient() != null) {
			$feed->setHttpClient($this->getHttpClient());
		}
		$etag = $response->getHeader('ETag');
		if ($etag !== null) {
			$feed->setEtag($etag);
		}
		return $feed;
	}


	/**
	 * Imports a feed represented by $string.
	 *
	 * @param string $string
	 * @param string $className The class which is used as the return type
	 * @param integer $majorProcolVersion (optional) The major protocol version
	 *        of the data model object that is to be created.
	 * @param integer $minorProcolVersion (optional) The minor protocol version
	 *        of the data model object that is to be created.
	 * @throws Zend_Gdata_App_Exception
	 * @return Zend_Gdata_App_Feed
	 */
	public static function importString($string,
	$className='Zend_Gdata_App_Feed', $majorProtocolVersion = null,
	$minorProtocolVersion = null)
	{
		// Load the feed as an XML DOMDocument object
		@ini_set('track_errors', 1);
		$doc = new DOMDocument();
		$success = @$doc->loadXML($string);
		@ini_restore('track_errors');

		if (!$success) {
			require_once 'Zend/Gdata/App/Exception.php';
			throw new Zend_Gdata_App_Exception(
                "DOMDocument cannot parse XML: $php_errormsg");
		}

		$feed = new $className();
		$feed->setMajorProtocolVersion($majorProtocolVersion);
		$feed->setMinorProtocolVersion($minorProtocolVersion);
		$feed->transferFromXML($string);
		$feed->setHttpClient(self::getstaticHttpClient());
		return $feed;
	}


	/**
	 * Imports a feed from a file located at $filename.
	 *
	 * @param  string $filename
	 * @param  string $className The class which is used as the return type
	 * @param  string $useIncludePath Whether the include_path should be searched
	 * @throws Zend_Gdata_App_Exception
	 * @return Zend_Gdata_App_Feed
	 */
	public static function importFile($filename,
	$className='Zend_Gdata_App_Feed', $useIncludePath = false)
	{
		@ini_set('track_errors', 1);
		$feed = @file_get_contents($filename, $useIncludePath);
		@ini_restore('track_errors');
		if ($feed === false) {
			require_once 'Zend/Gdata/App/Exception.php';
			throw new Zend_Gdata_App_Exception(
                "File could not be loaded: $php_errormsg");
		}
		return self::importString($feed, $className);
	}

	/**
	 * GET a URI using client object.
	 *
	 * @param string $uri GET URI
	 * @param array $extraHeaders Extra headers to add to the request, as an
	 *        array of string-based key/value pairs.
	 * @throws Zend_Gdata_App_HttpException
	 * @return Zend_Http_Response
	 */
	public function get($uri, $extraHeaders = array())
	{
		$requestData = $this->prepareRequest('GET', $uri, $extraHeaders);
		return $this->performHttpRequest(
		$requestData['method'], $requestData['url'],
		$requestData['headers']);
	}

	/**
	 * POST data with client object
	 *
	 * @param mixed $data The Zend_Gdata_App_Entry or XML to post
	 * @param string $uri POST URI
	 * @param array $headers Additional HTTP headers to insert.
	 * @param string $contentType Content-type of the data
	 * @param array $extraHeaders Extra headers to add to the request, as an
	 *        array of string-based key/value pairs.
	 * @return Zend_Http_Response
	 * @throws Zend_Gdata_App_Exception
	 * @throws Zend_Gdata_App_HttpException
	 * @throws Zend_Gdata_App_InvalidArgumentException
	 */
	public function post($data, $uri = null, $remainingRedirects = null,
	$contentType = null, $extraHeaders = null)
	{
		$requestData = $this->prepareRequest(
            'POST', $uri, $extraHeaders, $data, $contentType);
		return $this->performHttpRequest(
		$requestData['method'], $requestData['url'],
		$requestData['headers'], $requestData['data'],
		$requestData['contentType']);
	}

	/**
	 * PUT data with client object
	 *
	 * @param mixed $data The Zend_Gdata_App_Entry or XML to post
	 * @param string $uri PUT URI
	 * @param array $headers Additional HTTP headers to insert.
	 * @param string $contentType Content-type of the data
	 * @param array $extraHeaders Extra headers to add to the request, as an
	 *        array of string-based key/value pairs.
	 * @return Zend_Http_Response
	 * @throws Zend_Gdata_App_Exception
	 * @throws Zend_Gdata_App_HttpException
	 * @throws Zend_Gdata_App_InvalidArgumentException
	 */
	public function put($data, $uri = null, $remainingRedirects = null,
	$contentType = null, $extraHeaders = null)
	{
		$requestData = $this->prepareRequest(
            'PUT', $uri, $extraHeaders, $data, $contentType);
		return $this->performHttpRequest(
		$requestData['method'], $requestData['url'],
		$requestData['headers'], $requestData['data'],
		$requestData['contentType']);
	}

	/**
	 * DELETE entry with client object
	 *
	 * @param mixed $data The Zend_Gdata_App_Entry or URL to delete
	 * @return void
	 * @throws Zend_Gdata_App_Exception
	 * @throws Zend_Gdata_App_HttpException
	 * @throws Zend_Gdata_App_InvalidArgumentException
	 */
	public function delete($data, $remainingRedirects = null)
	{
		if (is_string($data)) {
			$requestData = $this->prepareRequest('DELETE', $data);
		} else {
			$headers = array();

			$requestData = $this->prepareRequest(
                'DELETE', null, $headers, $data);
		}
		return $this->performHttpRequest($requestData['method'],
		$requestData['url'],
		$requestData['headers'],
                                         '',
		$requestData['contentType'],
		$remainingRedirects);
	}

	/**
	 * Inserts an entry to a given URI and returns the response as a
	 * fully formed Entry.
	 *
	 * @param mixed  $data The Zend_Gdata_App_Entry or XML to post
	 * @param string $uri POST URI
	 * @param string $className The class of entry to be returned.
	 * @param array $extraHeaders Extra headers to add to the request, as an
	 *        array of string-based key/value pairs.
	 * @return Zend_Gdata_App_Entry The entry returned by the service after
	 *         insertion.
	 */
	public function insertEntry($data, $uri, $className='Zend_Gdata_App_Entry',
	$extraHeaders = array())
	{
		$response = $this->post($data, $uri, null, null, $extraHeaders);

		$returnEntry = new $className($response->getBody());
		$returnEntry->setHttpClient(self::getstaticHttpClient());

		$etag = $response->getHeader('ETag');
		if ($etag !== null) {
			$returnEntry->setEtag($etag);
		}

		return $returnEntry;
	}

	/**
	 * Update an entry
	 *
	 * @param mixed $data Zend_Gdata_App_Entry or XML (w/ID and link rel='edit')
	 * @param string|null The URI to send requests to, or null if $data
	 *        contains the URI.
	 * @param string|null The name of the class that should be deserialized
	 *        from the server response. If null, then 'Zend_Gdata_App_Entry'
	 *        will be used.
	 * @param array $extraHeaders Extra headers to add to the request, as an
	 *        array of string-based key/value pairs.
	 * @return Zend_Gdata_App_Entry The entry returned from the server
	 * @throws Zend_Gdata_App_Exception
	 */
	public function updateEntry($data, $uri = null, $className = null,
	$extraHeaders = array())
	{
		if ($className === null && $data instanceof Zend_Gdata_App_Entry) {
			$className = get_class($data);
		} elseif ($className === null) {
			$className = 'Zend_Gdata_App_Entry';
		}

		$response = $this->put($data, $uri, null, null, $extraHeaders);
		$returnEntry = new $className($response->getBody());
		$returnEntry->setHttpClient(self::getstaticHttpClient());

		$etag = $response->getHeader('ETag');
		if ($etag !== null) {
			$returnEntry->setEtag($etag);
		}

		return $returnEntry;
	}

	/**
	 * Provides a magic factory method to instantiate new objects with
	 * shorter syntax than would otherwise be required by the Zend Framework
	 * naming conventions.  For instance, to construct a new
	 * Zend_Gdata_Calendar_Extension_Color, a developer simply needs to do
	 * $gCal->newColor().  For this magic constructor, packages are searched
	 * in the same order as which they appear in the $_registeredPackages
	 * array
	 *
	 * @param string $method The method name being called
	 * @param array $args The arguments passed to the call
	 * @throws Zend_Gdata_App_Exception
	 */
	public function __call($method, $args)
	{
		if (preg_match('/^new(\w+)/', $method, $matches)) {
			$class = $matches[1];
			$foundClassName = null;
			foreach ($this->_registeredPackages as $name) {
				try {
					// Autoloading disabled on next line for compatibility
					// with magic factories. See ZF-6660.
					if (!class_exists($name . '_' . $class, false)) {
						require_once 'Zend/Loader.php';
						@Zend_Loader::loadClass($name . '_' . $class);
					}
					$foundClassName = $name . '_' . $class;
					break;
				} catch (Zend_Exception $e) {
					// package wasn't here- continue searching
				}
			}
			if ($foundClassName != null) {
				$reflectionObj = new ReflectionClass($foundClassName);
				$instance = $reflectionObj->newInstanceArgs($args);
				if ($instance instanceof Zend_Gdata_App_FeedEntryParent) {
					$instance->setHttpClient($this->_httpClient);

					// Propogate version data
					$instance->setMajorProtocolVersion(
					$this->_majorProtocolVersion);
					$instance->setMinorProtocolVersion(
					$this->_minorProtocolVersion);
				}
				return $instance;
			} else {
				require_once 'Zend/Gdata/App/Exception.php';
				throw new Zend_Gdata_App_Exception(
                        "Unable to find '${class}' in registered packages");
		}
	} else {
		require_once 'Zend/Gdata/App/Exception.php';
		throw new Zend_Gdata_App_Exception("No such method ${method}");
}
    }

    /**
     * Retrieve all entries for a feed, iterating through pages as necessary.
     * Be aware that calling this function on a large dataset will take a
     * significant amount of time to complete. In some cases this may cause
     * execution to timeout without proper precautions in place.
     *
     * @param $feed The feed to iterate through.
     * @return mixed A new feed of the same type as the one originally
     *          passed in, containing all relevent entries.
     */
    public function retrieveAllEntriesForFeed($feed) {
    	$feedClass = get_class($feed);
    	$reflectionObj = new ReflectionClass($feedClass);
    	$result = $reflectionObj->newInstance();
    	do {
    		foreach ($feed as $entry) {
    			$result->addEntry($entry);
    		}

    		$next = $feed->getLink('next');
    		if ($next !== null) {
    			$feed = $this->getFeed($next->href, $feedClass);
    		} else {
    			$feed = null;
    		}
    	}
    	while ($feed != null);
    	return $result;
    }

    /**
     * This method enables logging of requests by changing the
     * Zend_Http_Client_Adapter used for performing the requests.
     * NOTE: This will not work if you have customized the adapter
     * already to use a proxy server or other interface.
     *
     * @param $logfile The logfile to use when logging the requests
     */
    public function enableRequestDebugLogging($logfile)
    {
    	$this->_httpClient->setConfig(array(
            'adapter' => 'Zend_Gdata_App_LoggingHttpClientAdapterSocket',
            'logfile' => $logfile
    	));
    }

    /**
     * Retrieve next set of results based on a given feed.
     *
     * @param Zend_Gdata_App_Feed $feed The feed from which to
     *          retreive the next set of results.
     * @param string $className (optional) The class of feed to be returned.
     *          If null, the next feed (if found) will be the same class as
     *          the feed that was given as the first argument.
     * @return Zend_Gdata_App_Feed|null Returns a
     *          Zend_Gdata_App_Feed or null if no next set of results
     *          exists.
     */
    public function getNextFeed($feed, $className = null)
    {
    	$nextLink = $feed->getNextLink();
    	if (!$nextLink) {
    		return null;
    	}
    	$nextLinkHref = $nextLink->getHref();

    	if ($className === null) {
    		$className = get_class($feed);
    	}

    	return $this->getFeed($nextLinkHref, $className);
    }

    /**
     * Retrieve previous set of results based on a given feed.
     *
     * @param Zend_Gdata_App_Feed $feed The feed from which to
     *          retreive the previous set of results.
     * @param string $className (optional) The class of feed to be returned.
     *          If null, the previous feed (if found) will be the same class as
     *          the feed that was given as the first argument.
     * @return Zend_Gdata_App_Feed|null Returns a
     *          Zend_Gdata_App_Feed or null if no previous set of results
     *          exists.
     */
    public function getPreviousFeed($feed, $className = null)
    {
    	$previousLink = $feed->getPreviousLink();
    	if (!$previousLink) {
    		return null;
    	}
    	$previousLinkHref = $previousLink->getHref();

    	if ($className === null) {
    		$className = get_class($feed);
    	}

    	return $this->getFeed($previousLinkHref, $className);
    }

    /**
     * Returns the data for an If-Match header based on the current Etag
     * property. If Etags are not supported by the server or cannot be
     * extracted from the data, then null will be returned.
     *
     * @param boolean $allowWeak If false, then if a weak Etag is detected,
     *        then return null rather than the Etag.
     * @return string|null $data
     */
    public function generateIfMatchHeaderData($data, $allowWeek)
    {
    	$result = '';
    	// Set an If-Match header if an ETag has been set (version >= 2 only)
    	if ($this->_majorProtocolVersion >= 2 &&
    	$data instanceof Zend_Gdata_App_Entry) {
    		$etag = $data->getEtag();
    		if (($etag !== null) &&
    		($allowWeek || substr($etag, 0, 2) != 'W/')) {
    			$result = $data->getEtag();
    		}
    	}
    	return $result;
    }

    /**
     * Determine whether service object is using XML to object mapping.
     *
     * @return boolean True if service object is using XML to object mapping,
     *                 false otherwise.
     */
    public function usingObjectMapping()
    {
    	return $this->_useObjectMapping;
    }

    /**
     * Enable/disable the use of XML to object mapping.
     *
     * @param boolean $value Pass in true to use the XML to object mapping.
     *                       Pass in false or null to disable it.
     * @return void
     */
    public function useObjectMapping($value)
    {
    	if ($value === True) {
    		$this->_useObjectMapping = true;
    	} else {
    		$this->_useObjectMapping = false;
    	}
    }

}
